1. Field of the Invention
The invention relates to a method for the manufacture of composite foam materials of foam-material flakes, polyurethane binders and additional solid components which cause a modification or change of the properties of the composite foam material.
2. Description of the Prior Art
In a known method for the manufacture of composite foam materials, flakes of foam-material remnants, as a rule of soft elastic polyurethane foam materials, are mixed with binders which are likewise based on polyurethane raw materials and are joined together under pressure and optionally heat. In general one works here with isocyanate group-containing prepolymers as binders and the hardening is crried out by means of hot steam which serves as the heat carrier and at the same time as a cross-linking agent for the prepolymer.
While the properties of the composite foam materials obtained in this manner are adequate for a number of rather secondary applications, they do not allow in many cases the use of these products because, for instance, the elongation breaking point or tensile strength is too low. Also the appearance of such composite foam materials which are as a rule produced from random mixtures of flakes of foam materials with different colors leaves much to be desired and is improved in many cases by the addition of fairly large quantities of expensive pigment pastes to the binder. Therefore, simple and cost-effective methods are needed which impart to the composite foam materials so produced a uniform appearance.
From German Published Prosecuted Application No. 16 29 666 it is known that webs of non-thermoplastic foam materials can be given thermoplastic properties, i.e. can be made deformable and weldable by bringing small particles, i.e. flakes of the non-thermoplastic foam material mixed with thermoplastic plastic material into the form of a web, then densifying them by subjecting them to pressure and heat and then cooling them. To obtain good deformation and welding properties, however, relatively large quantities of the thermoplastic material with which the flakes are impregnated are required. It has been found that such composite materials are not sufficiently heat-resistant, since the charged-in foam material flakes revert under the influence of higher temperatures and thereby lead to dimensional changes or even to a decomposition of the composite web.
From U.S. Pat. No. 3,114,722, a method for the manufacture of composite foam materials is known in which the foam material flakes are first mixed with dispersions or solutions of a catalyst and subsequently with a prepolymer.
Methods for manufacturing composite foam materials from foam material flakes, polyurethane binders and additional solid components are known from U.S. Pat. No. 3,717,597 as well as from the report on the Japanese Patent Application No. 117,766/1975, reported in the CPI-Profit Booklet 1977, Report 89734 X/48. There, solid components are used which cause a modification or change of the properties of the composite foam materials. In this method, the foam material flakes are mixed with a binder which forms polyurethane, and with the additional solid components. The foam material flakes are cemented together by subsequent hardening of the mixture so obtained under pressure and, optionally heat.
In the known manufacturing methods for composite foam materials, the properties of the end products and therefore of the composite foam materials, are imparted essentially by the type of foam material flakes and the binder used. A modification or change of these properties is possible only at relatively large expense, since the additional solid components must generally be brought into the mixture of foam material flakes and the polyurethane binders by mechanical means and must be mixed homogeneously so that the composite foam materials produced therefrom have homogeneous and uniform properties throughout their entire volume.